Error 1603 is a typical Windows Installer error, and you may need to go through the log files to find out what may cause this.
Also note that Windows Server 2019 is not a supported host OS (which does not necessarily mean that it will not work).
see https://kb.vmware.com/s/article/2091273
Aside from this, is there a special reason, why you want to install the Windows based vCenter Server rather than the vCenter Server Virtual Appliance (vCSA)?
André
Installing vCenter Server on a Windows host was the initial deployment model, but it has changed, and VMware now provides a virtual appliance, which can be deployed on an ESXi host, i.e. no more need of a Windows Server. In fact, current versions do not offer the Windows based vCenter Server installation option anymore.
Please take a look at e.g. vCenter Server Installation and Setup for details about the installation.
Note that vCenter Server usually supports ESXi hosts of the same version, and the previous 2 versions only.
Since you mentioned version 6.5, and assuming the hosts that you want/need to manager run ESXi 6.5, you cannot use the latest vCenter Server version (which is 8.0) but have to go with version 7.0. Also remember that vSphere 6.x went out of support in October last year!
André
>>> WOW... we are way behind...
Short answer. Yes you are 😉
>>> You either are not entitled or do not have permissions to download this product
This message is usually not related to the version itself, but to the permissions that you have in the Customer Connect portal. You may need to reach out to your license admin to assign you download permissions.
André